Exposure device for transmitting light waves modulated to contain information

ABSTRACT

An exposure device for transmitting the output of a computer in the form of light waves modulated to contain information, for example, derived from the fluorescent surface of a cathode ray tube or the projector screen surface of a microfilm projector. A light transmission member is disposed between the fluorescent surface or the screen surface and the surface of the photosensitive member for transmitting the information, after being brightness modulated, to the surface of the photosensitive member. An adjusting member is provided to keep the distance between said surfaces at a constant and desired amount, so as to obtain a high quality image having a high resolving power and clearness.

United States Patent 1 Ichikawa EXPOSURE DEVICE FOR TRANSMITTING LIGHT WAVES MODULATED TO CONTAIN INFORMATION [75] Inventor: Junji Ichikawa, Yokohama, Japan [73] Assignee: Canon Kahushiki Kaisha, Tokyo,

Japan 22 Filed: May 9,1973

21 Appl. No.: 358,484

[30) Foreign Application Priority Data May 12, 1972 Japan 47-46988 June 12, 1972 Japan 47-58327 {56] References Cited UNITED STATES PATENTS 4/1965 Auyang et a1 350/96 R X 7/1967 Taillie 350/96 R OTHER PUBLICATIONS Fiber Optics A New Tool In Electronics," by Kro- 1 June 17, 1975 lak et al., Journal of the Smpte, Oct. 1960, Vol. 69, No. 10. Pg. 708.

Primary ExuminerRichard L. Moses Attorney, Agenl, or FirmFitzpatrick, Cella, Harper & Scinto [57] ABSTRACT An exposure device for transmitting the output of a computer in the form of light waves modulated to contain information, for example, derived from the fluorescent surface of a cathode ray tube or the projector screen surface of a microfilm projector. A light transmission member is disposed between the fluorescent surface or the screen surface and the surface of the photosensitive member for transmitting the information, after being brightness modulated, to the surface of the photosensitive member. An adjusting member is provided to keep the distance between said surfaces at a constant and desired amount, so as to obtain a high quality image having a high resolving power and clearness.

14 Claims, 5 Drawing Figures sum F l G.

PATENTEDJUN 1 7 1975 FIG. 2

PATENTEDJUN 17 1915 SEE? 1 EXPOSURE DEVICE FOR TRANSMITTING LIGHT WAVES MODULATED TO CONTAIN INFORMATION BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates generally to an exposure device for transmitting light waves modulated to contain information. There are various kinds of electrophotographic machines which have already been proposed and practiced, and the present invention relates more particularly to an exposure station of such electrophotographic machines, and the improvement resides in the use of a light transmission member to transmit light waves modulated to contain information so as to provide uniform and clear exposure of the light waves modulated to contain information.

2. Description of the Prior Art The assignee of this invention has proposed an improved electrophotographic process as described in the copending US. Patent application Ser. No. 317,783 filed on Dec, 22, 1972, in U.S.A. According to said electrophotographic process, an insulating surface layer of a photosensitive member comprising said insu lating layer, a photoconductive layer and a conductive base, is positively charged by a discharging-charging device when said photoconductive layer is of N-type photoconductivity or negatively charged when said photoconductive layer is of P-type photoconductivity, so as to form charges of a polarity opposite to said charges on the insulating layer in the vicinity of the interface between the photoconductive layer and the insulating layer. Then the charged insulating surface is brought into contact with a discharging-charging liquid having a desired potential (including grounded potential) predetermined to satisfy the condition d1 5 l/Cid, where d) is the specific resistivity, Ci is the electrostatic capacity of the insulating layer, d is the thickness of the liquid layer and l is the discharging or charging time, so as to charge or discharge the insulating surface and simultaneously therewith or right after, the insulating surface is exposed to a light image to vary the charge pattern of the photosensitive member in accordance with the light-and-dark pattern of the light image, and next, after the discharging-charging liquid is removed, the whole surface of the insulating layer is exposed to light so that the charges bound at said interface between the photoconductive layer and the insulating layer are released to form a high contrast electrostatic latent image on the surface of the photosensitive member. The latent image thus formed is liquid or dry developed by a developing agent mainly consisting of charged and colored particles to visualize the image, and the visualized image is transferred to a transfer member such as paper, utilizing an internal or external electric field. The transferred image is fixed on the transfer material by heating and drying using an infrared lamp, etc. On the other hand, after the transfer is finished, the surface of the insulating layer is cleaned to remove the retained toner so that the photosensitive member may be used repeatedly.

When a photosensitive member, consisting of an insulating layer, a photoconductive layer and an insulating layer or a four-layer member adding another conductive layer to said three layers, is used, the dischargingcharging liquid used in the above mentioned pro- 2 cess should have the property of d1 3 r C, C (TC 'd, where d) is the specific resistivity, C, and C are electrostatic capacities of said two insulating layers, respectively, d is the thickness of the liquid layer, and r is the charging or discharging time. This liquid is used at a desired potential. including grounded potential.

In the copending Japanese application No. l4 l 86/ l 972 of the same assignee, we have proposed an electrophotographic process, in which the surface of a photosensitive member comprising an insulating layer, a photoconductive layer and a conductive base is charged positively or negatively, and then the charged surface is discharged by a discharging electrode having electrical unevenness and simultaneously therewith or right after the surface is exposed to a light image, and next, if necessary, the whole surface of the insulating layer is exposed to a blanket radiation to obtain a high contrast electrostatic latent image on the insulating layer. The steps following said latent image forming process are substantially the same as the steps described previously.

ln the electrophotographic device, as mentioned heretofore, for exposing the surface of the photosensitive member to light waves modulated to contain information, particularly, for exposing light waves modulated to contain information from the fluorescent surface of a cathode ray tube or the projecting screen surface of a microfilm projector, or the output of a computer or the like, after being subjected to brightness modification, to the surface of a photosensitive member, it is necessary to dispose a light transmission member between the surfaces of the photosensitive member and the light display surface so as to transmit information.

When the light transmission member is used, one surface thereof is fixed to the fluorescent surface of the cathode ray tube or to the projection screen surface of the microfilm projector. The following two methods are conventional for exposing a light image on the photosensitive surface.

According to one method, the photosensitive member and the light transmission member are spaced apart by a predetermined distance, and light waves modulated to contain information are directed to the surface of the photosensitive member using a projection lens. According to the other method, the photosensitive member is placed at a position as close as possible to the light transmission member without deteriorating a desired resolving power and the light image is directly projected on the photosensitive member. In the latter method, it may be possible to intervene an optional liquid between the photosensitive member and the light transmission member. However, according to the first method, the loss of light is significant so that it is difficult to obtain a high contrast image. According to the second method, such a loss of light can be avoided because the distance between the photosensitive member and the light transmission member is very short, for example, about several 10 microns, and consequently, it is possible to obtain a high speed copying and high resolving power image. However, if the photosensitive member is a drum or belt, unevenness, i.e., concave or convex portions, of the surface of the photosensitive member becomes unavoidable due to the error in manufacturing the drum or belt, as well as eccentricity, thermal expansion, wearing and so on, so that the distance between the photosensitive member and the light transmission member varies, thereby varying the resolving power and the amount of light which deterio rates the quality of the recorded image. Further, the photosensitive member and the light transmission member tend to frictionally contact each other to damage the two members. Such degradation of clearness of the light image on the surface of the photosensitive member is caused by the fact that at the light image sending surface, the highest clearness is obtained but the clearness deteriorates due to the light dispersion as the distance from the sending surface becomes larger, so that variation in distance causes different degrees of clearness. For avoiding such disadvantages, attempts have been made to improve the manufacturing preci sion to eliminate the unevenness of the surface of the photosensitive member, but such working of the surface is very difficult and even if an ideal surface could be obtained, it is very difficult or even impossible to make the distance between the surface of the photosensitive member and the light transmission member uniform by mechanical means.

SUMMARY OF THE INVENTION This invention overcomes all of the above mentioned defects and provides an exposure device for the transmission of light waves modulated to contain information by applying the light so modulated from a cathode ray tube to the photosensitive member as an excellently clear light image.

Accordingly, the main object of this invention is to provide an improved light transmission device in which the distance from the light sending surface relative to the photosensitive member is always kept constant.

Another object of this invention is to provide an improved light transmission device wherein the photosensitive member is fixed and the light transmission member is freely movable relative to the photosensitive member so as to keep the distance therebetween always constant.

A further object of this invention is to provide an improved light transmission device in which the light transmission member is fixed and the photosensitive member is freely movable relative to the light transmission member so as to keep the distance therebetween always constant.

Said objects and other objects of this invention be come more apparent from the following description referring to the attached drawings,

BRIEF DESCRIPTION OF THE DRAWINGS FIGv l is a side elevational view illustrating one embodiment of the invention;

FIG. 2 is a plan view of the embodiment of FIG. 1;

FIG. 3 is a side elevational view illustrating another embodiment of the invention;

FIGv 4 shows a plan view of the embodiment of FIG. 3; and

FIG. is a cross sectional view taken along the lines \/,V and V -V in FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2, OFT tube 1 comprises a cathode ray tube 2 provided with an optical fibre plate 3 at its fluorescent surface. and 4 is a deflection coil. The light surface 3a of the optical fibre plate 3 and the surface ofa photosensitive member 5 have plain or curved surfaces so as to contact uniformly or closely approach each other. When a drum type photosensitive member is used, the light sending surface 3:: of the optical fibre plate 3 is preferably curved concentrically with the circumference of the photosensitive member. By this arrangement, the distance between the photosensitive member and the optical fibre plate or degree of the contact therebetween is adjusted to be always constant. The OFT tube 1 is fixedly secured to a base plate 8 by support members 6 and 7 and the center of said tube 1 is supported at the center of the drum 5.

The drum 5 is disposed to contact with or be closely adjacent the surface of the optical fibre plate, and the drum is rotatably mounted around a shaft 11 by a bearing holder 9 and a ball bearing 10.

A driven gear 12 is fixed to the bearing holder 9 and the driven gear I2 is driven by a driving gear 14 of a motor 13 to rotate the drum 5. The shaft 11 of the drum 5 is supported by a bearing 16 to a holder 15 fixed to the base plate 8. The bearing 16 is retained by the holder 15 in such a manner that the drum shaft 11 can be elastically movable in the direction of arrow AB by a spring 17, which is held by a member 18 fixed to the base plate 8. Between bearings 10 and 16, a spacer 19 is provided for eliminating the axial gap of the drum 5.

According to the above mentioned construction, the photosensitive drum is always urged toward the OFT tube side, however, it is not preferable that the drum and OFT tube frictionally contact each other, which would damage the respective surfaces, and consequently, adjusting parts are provided on both sides of the light display surface to keep the distance between the drum surface and the surface of the OFT tube at a predetermined constant amount.

Said adjusting parts comprise a retaining plate 20 fixedly mounted on the base plate 8 and a rotary shaft 22 having a ball bearing 21 mounted on the retaining plate 20, the center of the ball bearing 21 being positioned on the line connecting the center of the OFT tube and the center of the drum 5 and the peripheral surface of the ball bearing being contactable with both sides of the drum so that the distance between the displaying surface of the OFT tube and the peripheral surface of the ball bearing is kept at a desired amount Ar. In one form of the invention a lubricating liquid is interposed between the photosensitive member and the light transmission member.

In FIGS. 1 and 2, electrostatic latent image forming means, developing means, transferring means and cleaning means, which are to be arranged suitably around the circumference of the drum, are omitted to simplify the drawing.

Next, another embodiment will be explained referring to FIGS. 3 and 4. In FIGS. 3 and 4, OFT tube 23 comprises a cathode ray tube 24 and an optical fibre plate 25 provided at the fluorescent surface of the tube 24. A deflection coil is designated at 26. The light emitting surface 250 of the optical fibre plate 25 and the surface of the photosensitive drum 27 are plane or curved so that both surfaces contact uniformly or are closely adjacent with a predetermined distance from each other. When a drum type photosensitive member is used, the light emitting surface 25a of the intermediate fibre plate 25 is circularly curved concentric with the circumference of the drum. By this arrangement, the degree of contact of the two members or the distance between the two members is always kept con-- stant. The photosensitive drum is rotatably mounted around the shaft with the aid of a bearing holder 28 and a ball bearing 29.

On the bearing holder 28, a driven gear 31 is fixed. which is driven by a driving gear 33 of a motor 32 to rotate the photosensitive drum. The shaft 30 of the drum is supported by a bearing 36 on a holder 35, fixed to the base plate 34. Between bearings 29 and 36, a spacer 37 is provided for eliminating the axial gap of the drum. On the other hand, the optical fibre plate 25 is mounted in contact with or closely adjacent to the photosensitive drum surface. A movable plate 40 is mounted on transfer rollers 39 and 39, supported by members 38 and 38 fixed to the base plate 34. The OFT tube is supported by the supporting members and mounted on the movable plate 40, which is always urged toward the drum by a spring 42 provided on member 41.

As mentioned above, the OFT tube is always forced toward the drum surface, but for avoiding frictional contact of the surfaces, which will produce damages to the surfaces, adjusting parts are provided on both sides of the light display surface of the OFT tube for keeping constant and definite the distance between the two surfaces.

The adjusting parts comprise a retaining plate 43 mounted fixedly on the movable plate 40, and a rotary shaft 45 having a ball bearing 44 mounted on the plate 43, the center of the ball bearing being positioned on the line connecting the center of the OFT tube and the center of the photosensitive drum and the peripheral surface of the ball bearing being contactable with both sides of the photosensitive drum, so that the distance between the display surface of the tube and the peripheral surface of the ball bearing is kept at a constant amount Al. In one form of the invention a lubricating liquid is interposed between the photosensitive member and the OFT tube.

FIG. 5 shows a cross sectional view taken along the lines V,-\/ and V V in FIGS. 3 and 4. In FIG. 5, the bottom side portions of the movable plate 40 are inclined as shown and the movable plate 40 is movable on a definite rail with the transfer rollers 39 and 39.

In FIGS. 3 and 4, similar to FIGS. 1 and 2, electrostatic latent image forming means, developing means, transfer means and cleaning means and so on, which are to be arranged around the drum, are omitted for simplifying the explanation.

As explained in detail, the light transmission device of this invention provides an excellent copied image having a definite and clear resolving power by retaining the distance between the exhibit surface and the drum surface always equal and constant during the rotation of the drum.

In said embodiments, the photosensitive plate is shown as a drum type, but an endless belt type plate could also be used.

I claim:

1. An exposure device for recording light waves modulated to contain information comprising:

a photosensitive member, a source of light waves modulated to contain information, a light transmission member provided near said source; and

means for adjusting and maintaining the degree of contact or distance between the photosensitive member and the light transmission member;

LII

said adjusting means retaining the light transmission member freely movable relative to the photosensitive member; whereby said modulated light waves are transmittable through said transmission member and recordable on said photosensitive member with high resolving power and clearness,

2. An exposure device according to claim I, in which said light source and said light transmission member together constitute an OFT tube.

3. An exposure device according to claim 1, in which a lubricating liquid is interposed between the photosensitive member and the light transmission member.

4. An exposure device according to claim I, in which said light transmission member is an optical fibre plate.

5. An exposure device for recording light waves mod ulated to contain information comprising:

a photosensitive member;

means for retaining the photosensitive member at a fixed position and freely rotatable;

an OFT tube; and

means for retaining the OFT tube freely movable relative to the photosensitive member;

whereby said modulated light waves are recordable on said photosensitive member with high resolving power and clearness.

6. An exposure device according to claim 5, in which said means for retaining the OFT tube comprises:

a retaining member for retaining the OFT tube;

a guide member to guide the movement of the retain ing member toward the photosensitive member; and

a member for urging the retaining member toward the photosensitive member.

7. An exposure device according to claim 6, in which said urging means is a spring.

8. An exposure device according to claim 5, in which said means for retaining the OFT tube is a ball bearing contactible with the side edge portion of the photosensitive member.

9. An exposure device according to claim 5, in which a lubricating liquid is interposed between the photosen sitive member and the OFT tube.

10. An exposure device for recording light waves modulated to contain information comprising:

a drum-shaped photosensitive member:

an OFT tube;

means for retaining the axis of the drum-shaped photosensitive member freely movable relative to the OFT tube and freely rotatable; and

means for retaining the OFT tube at a fixed position;

whereby said modulated light waves are recordable on said photosensitive member with high resolving power and clearness.

11. An exposure device according to claim 10, in which said means for retaining the photosensitive member comprises:

a retaining member for retaining the photosensitive member freely rotatable relative to the OFT tube; and

a member for urging the photosensitive member to ward the OFT tube.

12. An exposure device according to claim II, in

which said urging member is a spring.

13. An exposure device according to claim 10, in which said OFT tube retaining means has a ball bearing contactible with the side edge portion of the photosensitive member.

14. An exposure device according to claim 10, in which a lubricating liquid is interposed between the photosensitive member and the OFT tube. 

1. An exposure device for recording light waves modulated to contain information comprising: a photosensitive member, a source of light waves modulated to contain information, a light transmission member provided near said source; and means for adjusting and maintaining the degree of contact or distance between the photosensitive member and the light transmission member; said adjusting means retaining the light transmission member freely movable relative to the photosensitive member; whereby said modulated light waves are transmittable through said transmission member and recordable on said photosensitive member with high resolving power and clearness.
 2. An exposure device according to claim 1, in which said light source and said light transmission member together constitute an OFT tube.
 3. An exposure device according to claim 1, in which a lubricating liquid is interposed between the photosensitive member and the light transmission member.
 4. An exposure device according to claim 1, in which said light transmission member is an optical fibre plate.
 5. An exposure device for recording light waves modulated to contain information comprising: a photosensitive member; means for retaining the photosensitive member at a fixed position and freely rotatable; an OFT tube; and means for retaining the OFT tube freely movable relative to the photosensitive member; whereby said modulated light waves are recordable on said photosensitive member with high resolving power and clearness.
 6. An exposure device according to claim 5, in which said means for retaining the OFT tube comprises: a retaining member for retaining the OFT tube; a guide member to guide the movement of the retaining member toward the photosensitive member; and a member for urging the retaining member toward the photosensitive member.
 7. An exposure device according to claim 6, in which said urging means is a spring.
 8. An exposure device according to claim 5, in which said means for retaining the OFT tube is a bAll bearing contactible with the side edge portion of the photosensitive member.
 9. An exposure device according to claim 5, in which a lubricating liquid is interposed between the photosensitive member and the OFT tube.
 10. An exposure device for recording light waves modulated to contain information comprising: a drum-shaped photosensitive member; an OFT tube; means for retaining the axis of the drum-shaped photosensitive member freely movable relative to the OFT tube and freely rotatable; and means for retaining the OFT tube at a fixed position; whereby said modulated light waves are recordable on said photosensitive member with high resolving power and clearness.
 11. An exposure device according to claim 10, in which said means for retaining the photosensitive member comprises: a retaining member for retaining the photosensitive member freely rotatable relative to the OFT tube; and a member for urging the photosensitive member toward the OFT tube.
 12. An exposure device according to claim 11, in which said urging member is a spring.
 13. An exposure device according to claim 10, in which said OFT tube retaining means has a ball bearing contactible with the side edge portion of the photosensitive member.
 14. An exposure device according to claim 10, in which a lubricating liquid is interposed between the photosensitive member and the OFT tube. 